1. Field of the Invention
The present invention relates to an information processing apparatus that receives or transmits contents requiring copyright protections.
2. Related Art
Along with the diffusion of computer networks and digitalization in recent years, products called digital information home appliances are widespread. Furthermore, with the starting of digital broadcasting, digital TV, set-top boxes and DVD recorders for digital broadcasting are expected to be more widely spread from now on. When these digital information home appliances are connected to a home network, users can enjoy the contents via the network, and this is beneficial for users.
The contents refer to various kinds of digital data, for example, audiovisual data such as MPEG2 or MPEG4, audio data, document data such as text data and still image data. The contents of this kind of digital data have an advantage in that the data can be easily copied without degradation. On the other hand, there is a problem that users must pay attention to the copyright of the contents. We assume a case of transmitting copyright-protected contents from a certain transmitter to a receiver. It is desirable that exchanges of copyright-protected contents are limited to within a certain range. For example, the contents are exchanged within a range of a legitimate right, such as within a range of private utilization as prescribed in the copyright law, or within a narrower range than the range prescribed by the law. Exchanges of the contents with a third party outside this range should be prohibited.
However, a transmission of audio and audiovisual data via a network has a risk of infringement on the copyright law. For example, in the case of transmitting copy-prohibited contents from a transmitter to a receiver, the data can be illegally copied with a device connected to the network, unless the transmitted contents are encrypted. Upon transferring the audio and audiovisual data by using the interne protocol (IP), a general technique of filtering and monitoring the data on the network is used. The use of this technique makes it possible for a user to filter and obtain arbitrary data transferred between a specific transmitter and a receiver. In other words, the user can efficiently collect only the contents excluding control information out of the data transmitted from the transmitter to the receiver.
Considering the user's convenience, it is important to provide a system in which the receiver can securely receive the desirable contents from transmitter. For example, according to the IP, if there is a device called a proxy server between a transmitter and a receiver, the following problems may occur. The proxy server blocks a request for contents transmitted from the receiver, just before the transmitter. The proxy server sends, on behalf of the receiver, a request for contents that are different from the contents requested by the receiver, to the transmitter. Furthermore, the proxy server sends a request for contents that are different from the contents requested by the receiver, to a different transmitter. In this way, the proxy server enables a receiver to receive contents that are different from the contents originally requested by the receiver.